Conventionally, as this type of pressure regulating reservoir, there is one disclosed in Patent Literature 1, for example. In the pressure regulating reservoir disclosed in Patent Literature 1, an in-cylinder passage and a cylinder seat face are formed in a cylinder (seat valve in Patent Literature 1) and a first valve element (valve in Patent Literature 1) arranged so as to be opposite to the cylinder seat face is brought into contact with and separates from the cylinder seat face, so that the in-cylinder passage is opened and closed. An intra-valve element passage is formed in the first valve element, an intra-valve element seat face is formed in the intra-valve element passage, and a second valve element (ball valve in Patent Literature 1) arranged in the intra-valve element passage is brought into contact with and separates from the intra-valve element seat face, so that the intra-valve element passage is opened and closed.